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Abstract:

Polysaccharide based hydrogel compositions and methods of making and
using the same are provided. The subject polysaccharide based hydrogel
compositions are prepared by combining a polysaccharide component with a
hydrophilic polymer and a cross-linking agent. Also provided are kits and
systems for use in preparing the subject compositions.

Claims:

1.-161. (canceled)

162. A hydrogel composition, comprising a polysaccharide substrate or
derivative thereof having a molecular weight of 160 Dalton to 80,300
Dalton and comprising at least two reactive nucleophilic groups; a
synthetic, hydrophilic polymer of a molecular weight of 200 Dalton to
100,000 Dalton and comprising at least two nucleophilic reactive groups;
and a crosslinking agent.

163. The composition of claim 162, wherein the polysaccharide substrate
is chitosan, carboxymethylcellulose, carboxymethylchitosan, or a
derivative thereof.

164. The composition of claim 163, wherein the polysaccharide substrate
has a molecular weight of less than or equal to 10,000 Dalton.

165. The composition of claim 163, wherein the polysaccharide substrate
has a degree of deacetylation of 30% to 100%.

166. The composition of claim 163, wherein the polysaccharide substrate
has a degree of deacetylation greater than or equal to 70%.

167. The composition of claim 162, wherein the synthetic hydrophilic
polymer substrate is a polyethylene glycol.

168. The composition of claim 167, wherein the polyethylene glycol is
multi-armed.

169. The composition of claim 167, wherein the polyethylene glycol has a
molecular weight of 10,000 Dalton to 30,000 Dalton.

170. The composition of claim 162, wherein the crosslinking agent is a
polyethylene glycol comprising at least two electrophilic active groups.

171. The composition of claim 170, wherein the polyethylene glycol has a
molecular weight of 10,000 Dalton to 30,000 Dalton.

172. The composition of claim 170, wherein the polyethylene glycol is
multi-armed.

173. The composition of claim 162, wherein the composition comprises a
thickening agent, a foaming agent, a biologically active agent, a
pharmaceutically active agent, a visualization agent, or a radiopaque
agent.

174. The composition of claim 162, wherein the polysaccharide substrate
is soluble in an aqueous solution.

175. The composition of claim 162, wherein the polysaccharide substrate
is soluble in an alkaline solution.

176. The composition of claim 162, wherein the polysaccharide substrate
is soluble in a solution with a concentration of at least 30 mM.

178. A hydrogel composition, comprising a polysaccharide or derivative
thereof having a molecular weight of 160 Dalton to 80,300 Dalton, a
degree of deacetylation greater or equal to 70%, and at least two
reactive nucleophilic groups, wherein the polysaccharide or derivative
thereof is soluble in an aqueous solution; a multifunctional,
polyethylene glycol polymer of a molecular weight of 5,000 Dalton to
30,000 Dalton, at least three arms, and comprising at least two
nucleophilic reactive groups; and a multifunctional, multi-armed
crosslinker of polyethylene glycol having a molecular weight of 5,000
Dalton to 30,000 Dalton, at least three arms and comprising at least two
electrophilic reactive groups.

179. The composition of claim 178, wherein the aqueous solution is
alkaline with a concentration of at least 30 mM.

180. A hydrogel composition, comprising a chitosan or derivative thereof
having a molecular weight of less than or equal to 5,000 Dalton, a degree
of deacetylation greater or equal to 70%, and at least two reactive
nucleophilic groups, wherein the chitosan or derivative thereof is
soluble in an aqueous solution; a multifunctional, polyethylene glycol
polymer of a molecular weight of 5,000 Dalton to 30,000 Dalton, at least
three arms, and comprising at least two nucleophilic reactive groups; and
a multifunctional, multi-armed crosslinker of polyethylene glycol having
a molecular weight of 5,000 Dalton to 30,000 Dalton, at least three arms
and comprising at least two electrophilic reactive groups; wherein the
hydrogel comprises ester groups to provide for deagradation via
hydrolysis.

181. The composition of claim 180, wherein the aqueous solution is
alkaline with a concentration of at least 30 mM.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional Application
No. 61/259,564, filed on Nov. 9, 2009, which is herein incorporated by
reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] Hydrogels are water-swollen networks of hydrophilic homopolymers or
copolymers. These networks may be formed by various techniques; however,
the most common synthetic route is the free radical polymerization of
vinyl monomers in the presence of a difunctional cross-linking agent and
a swelling agent. The resulting polymer exhibits both liquid-like
properties, attributable to the major constituent, water, and solid-like
properties due to the network formed by the cross-linking reaction. These
solid-like properties take the form of a shear modulus that is evident
upon deformation.

[0003] Hydrogels offer biocompatibility and have been shown to have
reduced tendency for inducing thrombosis, encrustation and inflammation
when used in medical devices. Unfortunately, the use of hydrogels in
biomedical device applications has been hindered by poor mechanical
performance. Many medical devices use hydrogels to improve device
biocompatibility; however, many hydrogels can only be used in coatings as
a result of insufficient mechanical performance for use as a bulk
polymer. Many hydrogels suffer from low modulus, low yield stress, and
low strength when compared to non-swollen polymer systems. Lower
mechanical properties result from the swollen nature of hydrogels and the
non-stress bearing nature of the swelling agent.

[0004] The state of the art hydrogel formulations do not adequately bind
to all types of tissue surfaces. Furthermore, many of the existing
hydrogel materials are not consistent in their ability to provide
hemostatic control. The potency of these materials is limited by
addressing one of the many qualities that are desirable in a hydrogel
biomaterial (e.g. hemostasis or acting as an adhesion barrier, or
providing infection control, or eliciting a minimal tissue response). A
hydrogel biomaterial that addresses these multiple qualities consistently
is not currently available in the art.

[0005] As such, there is a continuing need to develop new compositions
capable of forming biocompatible hydrogel structures that offer improved
therapeutic outcomes.

[0011] Polysaccharide based hydrogel compositions and methods of making
and using the same are provided. The subject polysaccharide based
hydrogel compositions are prepared by combining a polysaccharide
component with a hydrophilic polymer and a cross-linking agent. Also
provided are kits and systems for use in preparing the subject
compositions.

[0012] These and other objects, advantages, and features of the invention
will become apparent to those persons skilled in the art upon reading the
details of the disclosure as more fully described below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention is best understood from the following detailed
description when read in conjunction with the accompanying drawings. It
is emphasized that, according to common practice, the various features of
the drawings are not to-scale. On the contrary, the dimensions of the
various features are arbitrarily expanded or reduced for clarity.
Included in the drawings are the following figures.

[0014]FIG. 1 shows a matrix of an exemplary polysaccharide based
hydrogel.

[0019]FIG. 6 shows an exemplary composition of a
PEG-PEG-carboxymethylcellulose hydrogel.

[0020] FIG. 7 shows an exemplary composition of a PEG-PEG-chitosan
hydrogel cryomilled into a particulate form.

[0021]FIG. 8 shows an exemplary composition of a freeze-dried
PEG-PEG-chitosan hydrogel rolled into a tube and held by a pair of
forceps.

[0022]FIG. 9. shows an exemplary composition of a shape-memory embodiment
of a PEG-PEG-chitosan hydrogel in the dry and hydrated states.

[0023]FIG. 10 shows an exemplary composition of a PEG-PEG-chitosan
hydrogel applied as a spray in a thin coating to a human palm.

[0024]FIG. 11 shows a cross-sectional view of a bovine tendon coated with
an exemplary composition of a PEG-PEG-chitosan hydrogel.

[0025]FIG. 12 shows a perspective view of a spray coating of an exemplary
composition of a PEG-glutaraldehyde-chitosan hydrogel applied to a human
hand.

[0026] FIG. 13 shows a cross-sectional view of an exemplary composition of
a freeze-dried PEG-PEG-chitosan hydrogel coated with an exemplary
composition of a PEG-PEG-chitosan hydrogel.

[0027] FIG. 14 shows a cross-sectional view of an exemplary composition of
a freeze-dried PEG-PEG-chitosan hydrogel coated with an exemplary
composition of a PEG-PEG-chitosan hydrogel doubled on itself and held in
a pair of forceps.

[0028]FIG. 15 shows a hollow chamber formed from an exemplary composition
of a PEG-PEG-chitosan hydrogel.

DETAILED DESCRIPTION OF THE INVENTION

[0029] Before the present invention is described, it is to be understood
that this invention is not limited to particular embodiments described,
as such may, of course, vary. It is also to be understood that the
terminology used herein is for the purpose of describing particular
embodiments only, and is not intended to be limiting, since the scope of
the present invention will be limited only by the appended claims.

[0030] Where a range of values is provided, it is understood that each
intervening value, to the tenth of the unit of the lower limit unless the
context clearly dictates otherwise, between the upper and lower limits of
that range is also specifically disclosed. Each smaller range between any
stated value or intervening value in a stated range and any other stated
or intervening value in that stated range is encompassed within the
invention. The upper and lower limits of these smaller ranges may
independently be included or excluded in the range, and each range where
either, neither or both limits are included in the smaller ranges is also
encompassed within the invention, subject to any specifically excluded
limit in the stated range. Where the stated range includes one or both of
the limits, ranges excluding either or both of those included limits are
also included in the invention.

[0031] Unless defined otherwise, all technical and scientific terms used
herein have the same meaning as commonly understood by one of ordinary
skill in the art to which this invention belongs. Although any methods
and materials similar or equivalent to those described herein can be used
in the practice or testing of the present invention, some potential and
preferred methods and materials are now described. All publications
mentioned herein are incorporated herein by reference to disclose and
describe the methods and/or materials in connection with which the
publications are cited. It is understood that the present disclosure
supersedes any disclosure of an incorporated publication to the extent
there is a contradiction.

[0032] It must be noted that as used herein and in the appended claims,
the singular forms "a", "an", and "the" include plural referents unless
the context clearly dictates otherwise. Thus, for example, reference to
"a compound" includes a plurality of such compounds and reference to "the
polymer" includes reference to one or more polymer and equivalents
thereof known to those skilled in the art, and so forth.

[0033] The publications discussed herein are provided solely for their
disclosure prior to the filing date of the present application. Nothing
herein is to be construed as an admission that the present invention is
not entitled to antedate such publication by virtue of prior invention.
Further, the dates of publication provided may be different from the
actual publication dates which may need to be independently confirmed.

Introduction

[0034] In general, the present invention includes hydrogel compositions
that have been fabricated out of a polysaccharide and two or more
additional components. The subject hydrogel compositions are
characterized by being capable of bonding tissue in both wet (e.g.,
blood) and dry environments, where adhesion of the composition to the
tissue is physiologically acceptable. A further feature of the subject
compositions is that they are well tolerated and do not elicit a
substantial inflammatory response, if any inflammatory response. The
subject compositions can provide multiple desirable qualities such as a
combination of any of the following: hemostatic properties, adhesive
properties, re-vascularization, biocompatibility, bactericidal,
bacteriostatic and/or fungicidal properties, tissue remodeling and/or
provides a scaffold for tissue engineering, regeneration, and/or cell
seeding, enzymatic or hydrolytic degradation pathways, swelling,
engineered residence times, engineered viscosities, temperature or energy
activation, inclusion of agents to enable visualization under imaging
modalities (X-ray, CT, MRI, US, PET, CTA, etc.), engineered degree of
hydrophilicity or hydrophobicity, gap and/or space filling, surface
coating, ability to absorb energy, inclusion of foaming agents, inclusion
of visual agents, ability to act as a drug delivery platform, media for
sound transmission, and engineered durometer.

[0035] The subject polysaccharide based hydrogel compositions are prepared
by combining or mixing a polysaccharide element and two ore more
components, such as a polymer and a cross-linking agent. An exemplary
matrix is provided in FIG. 1. Each of these precursor components or
compositions is now reviewed separately in greater detail.

Compositions

[0036] As noted above, the compositions of the present invention include a
polysaccharide component. Examples of polysaccharides suitable for use
with the present invention include, but are not limited to, chitosan,
hyaluronic acid, the family of chondroitin sulfates, heparin, keratan
sulfate, glycogen, glucose, amylase, amylopectin and derivatives thereof.
The polysaccharide may be naturally occurring or synthetically produced.
Polysaccharides have several reactive groups that are available for
chemical modification. These include the hydroxyl (OH), carboxyl (COOH),
and acetamido (COCH3) groups. Further functionality can be imparted
to specific polysaccharides in the form of an amine (NH2) group via
basic deacetylation, in which a polysaccharide is exposed to basic
conditions at elevated temperatures. The degree of deacetylation is
dependent on the strength of the alkaline conditions, the temperature of
the reaction environment, and the duration of the reaction. For example,
the percentage of deacetylation can be controlled to obtain different
chitosan molecules from a single source of chitin. Other methods of
imparting functionality onto polysaccharides are known to the art, such
as the functionalizing of native hyaluronic acid with amine groups
through the use of a hydrazide as taught by Prestwich and Marecak in U.S.
Pat. No. 5,874,417, which is herein incorporated by reference. In this
method, the carboxyl group of the disaccharide is linked to a
multi-functional hydrazide under acidic conditions in the presence of a
soluble carbodiimide.

[0037] In certain embodiments, the polysaccharide is chitosan. Chitosan is
a disaccharide formed through the deacetylation of chitin, a naturally
occurring material found in crustacean shells and some fungi. Chitosan is
a biocompatible, hydrophilic polymer with hemostatic and antimicrobial
characteristics. The Chitosan may be from a natural occurring source or
may be synthetically derived. Chitosan is described in detail is U.S.
Pat. Nos. 5,836,970, 5,599,916, and 6,444,797, the disclosures of which
are incorporated by reference herein in their entirety.

[0038] The non-polysaccharide components of the hydrogel material may
include a hydrophilic polymer such as any of the following natural,
synthetic, or hybrid polymers: poly(ethylene glycol), poly(ethylene
oxide), poly(vinyl alcohol), poly(allyl alcohol), poly(vinylpyrrolidone),
poly(alkylene oxides), poly(oxyethylated polyols), poly(ethyleneimine),
poly(allylamine), poly(vinyl amine), poly(aminoacids),
poly(ethyloxazoline), poly(ethylene oxide)-co-poly(propylene oxide) block
copolymers, polysaccharides, carbohydrates, oligopeptides, and
polypeptides. The polymer chains may include homo-, co-, or terpolymers
of the above materials, in a linear or branched form, and derivatives
thereof. These materials may crosslink into a hydrogel through the
formation of covalent bonds through the action of chemically active
groups that are present on the polysaccharide and the counterpart
hydrophilic polymers. Among the chemically active groups that are
preferred for use in the present invention are those that can form a
covalent bond with the readily available nucleophilic or electrophilic
residues.

[0039] Examples of electrophilic groups that can react with the
nucleophilic groups present on component materials include but are not
limited to carboxyl groups, isocyanates, thiocyanates,
N-hydroxysuccinimide esters, glycidyl ethers, glycidyl epoxides, vinyl
sulfones, maleimides, orthopyridyl disulfides, iodoacetamides, and
carbodiimides. Examples of nucleophilic groups that can react with the
electrophilic groups present on the component materials include but are
not limited to anhydrides, primary, secondary, tertiary, or quaternary
amines, amides, urethanes, ureas, hydrazides, sulfahydryl groups, or
thiols. The preceding list of reactive groups serves as an illustrative
example; extension to other nucleophilic and electrophilic moieties
should be clear to those of skill in the art.

[0040] In one embodiment, the hydrogel composition is a three-component
hydrogel that includes a multifunctional PEG with terminal nucleophilic
groups, a multifunctional PEG with terminal electrophilic groups, and
chitosan. When the polymeric components are reconstituted with the
appropriate buffers and mixed, they react to form a cohesive hydrogel.

[0041] The multifunctional PEG with terminal nucleophilic groups may
comprise a difunctionally activated, trifunctionally activated,
tetrafunctionally activated, or a star-branched activated polymer. The
molecular weight of the multifunctional nucleophilic PEG may be in the
range of 1 kiloDalton (kD) to 100 kD; the range of 5 kD to 40 kD; or the
range of 10 kD to 20 kD. The multifunctional nucleophilic PEG mass be
present in mass percentages of at least 1%; at least 5%; at least 10%; at
least 20%; at least 40%; at least 80%; at least 99%.

[0042] The multifunctional PEG with terminal electrophilic groups may
comprise difunctionally activated, trifunctionally activated,
tetrafunctionally activated, or a star-branched activated polymer. The
molecular weight of the multifunctional electrophilic PEG may be in the
range of 1 kD to 100 kD; the range of 5 kD to 40 kD; or the range of 10
kD to 20 kD. The multifunctional electrophilic PEG mass be present in
mass percentages of at least 1%; at least 5%; at least 10%; at least 20%;
at least 40%; at least 80%; at least 99%.

[0043] The polysaccharide (e.g., chitosan) may be present in a salt or
amine form. The chitosan may have a molecular weight in the range of 10
Dalton to 1 kD; the range of 1 kD to 10 kD; the range of 10 kD to 100 kD;
the range of 100 kD to 250 kD; the range of 250 kD to 500 kD; or the
range of 500 kD to 1000 kD. The chitosan may have a degree of
deacetylation in the range of 1% to 10%; the range of 10% to 20%; the
range of 20% to 30%; the range of 30% to 40%; the range of 40% to 50%;
the range of 50% to 60%; the range of 60% to 70%; the range of 70% to
80%; the range of 80% to 90%; or the range of 90% to 99%. The chitosan
may be present in the set hydrogel in a mass percentage range of 0.01% to
0.1%; a range of 0.1% to 0.5%; a range of 0.5% to 1.0%; a range of 1.0%
to 5%; a range of 5% to 10%; a range of 10% to 20%; a range of 20% to
40%; a range of 40% to 80%; or a range of 80% to 99%. In certain
embodiments, the polysaccharide is chitosan. In further embodiments, the
chitosan may also comprise a derivative of chitosan, such as N,O
carboxymethylchitosan as described in U.S. Pat. No. 5,888,988 the
disclosure of which is incorporated herein by reference in its entirety,
or a dicarboxyl derivatized chitosan as described in WO 2009/028965 the
disclosures of which are incorporated herein by reference in their
entirety. For example, dicarboxyl derivatized chitosan may be crosslinked
to a polyethylene glycol with at least two nucleophilic reactive groups
via a polyethylene glycol with at least two electrophilic reactive
groups.

[0044] Hydrolytically degradable linkages may be incorporated into the
backbone of the multifunctional PEG polymers. The inclusion of
hydrolytically degradable chemical groups enables the resulting hydrogel
to degrade after implantation in a controlled, consistent manner. The
chemical groups that border the hydrolytically degradable linkages
influence the rate of the hydrolysis reaction. Braunova et. al. (Collect.
Czech. Chem. Commun. 2004, 69, 1643-1656) have shown that the rate of
hydrolysis of ester bonds in poly(ethylene glycol) polymers decreases as
the number of methylene groups that border the ester bond is increased.
For example, a copolymer of trilysine and a multi-armed poly(ethylene
glycol) succinimidyl succinate will degrade in approximately 8 days in
aqueous media under physiological conditions. As shown in FIG. 2, the
succinimidyl succinate has two methyl groups located next to the
hydrolytically susceptible ester bond.

[0045] By way of comparison, a copolymer of trilysine and a multi-armed
poly(ethylene glycol) succinimidyl glutarate will degrade in
approximately 50 days in aqueous media under physiological conditions. As
shown in FIG. 3, the succinimidyl glutarate has three methyl groups
located next to the hydrolytically susceptible ester bond.

[0046] As the number of methyl groups neighboring the ester bond
increases, the rate of hydrolysis of the ester bond decreases. Further
decreases in the rate of hydrolysis of the ester bond should be attained
by increasing the number of methyl groups in the PEG polymer along the
following progression: PEG succinimidyl adipate, PEG succinimidyl
pimelate, PEG succinimidyl suberate, PEG succinimidyl azelate, PEG
succinimidyl sebacate, etc. The extension of this method of controlling
degradation times to other systems should be readily accessible to one of
skill in the art.

[0047] Another form of the invention is a three-component hydrogel
comprised of a multifunctional PEG with terminal nucleophilic groups, an
aldehyde component, and chitosan. When the polymeric components are
reconstituted with the appropriate buffers and mixed, they react to form
a cohesive hydrogel.

[0048] The nucleophilic PEG and polysaccharide (e.g., chitosan) components
in the composition are as described earlier. The aldehyde component in
the composition as provided herein can be any biocompatible aldehyde with
low toxicity. In particular, the aldehyde component includes a
di-aldehyde, a polyaldehyde or a mixture thereof. The examples of the
aldehyde include, but are not limited to, glyoxal, chondroitin sulfate
aldehyde, succinaldehyde, glutaraldehyde, and malealdehyde. In some
embodiments, the aldehyde component is glutaraldehyde. Other suitable
aldehydes which have low toxicity include multifunctional aldehydes
derived from naturally-occurring substances, e.g., dextrandialdehyde, or
saccharides. The aldehyde component can be an aldehyde product obtained
by an oxidative cleavage of carbohydrates and their derivatives with
periodate, ozone or the like. The aldehyde may optionally be pre-treated
with heat. See U.S. Pat. No. 7,303,757 by Schankereli for "Biocompatible
phase invertable proteinaceous compositions and methods for making and
using the same". The aldehyde component can be analyzed for properties
such as, viscosity, and osmolality. The aldehyde component of an adhesive
composition can itself be further comprised of components and/or
sub-components. Thus, the aldehyde component can be described in terms of
weight, weight-to-weight, weight-to-volume, or volume-to-volume, either
before or after mixing. For example, a polysaccharide may be crosslinked
to a multifunctional synthetic polymer with at least two reactive
nucleophilic groups via a dextran derivatized with aldehyde groups.

[0049] In some embodiments, the aldehyde component comprises of about
1-90% aldehyde concentration. In some embodiments, the aldehyde component
comprises of about 1-75% aldehyde concentration. In some embodiments, the
aldehyde component comprises of about 5-75% aldehyde concentration; about
10-75% aldehyde concentration; about 20-75% aldehyde concentration; about
30-75% aldehyde concentration; about 40-75% aldehyde concentration; about
50-75% aldehyde concentration; or about 60-75% aldehyde concentration.

[0050] The composition can comprise at least about 1% aldehyde
concentration; at least about 5% aldehyde concentration; at least about
10% aldehyde concentration; at least about 20% aldehyde concentration; at
least about 30% aldehyde concentration; at least about 40% aldehyde
concentration; at least about 50% aldehyde concentration; at least about
60% aldehyde concentration; at least about 70% aldehyde concentration; at
least about 80% aldehyde concentration; at least about 90% aldehyde
concentration; or at least about 99% aldehyde concentration. In some
embodiments, the adhesive composition comprises of about 1-30%, about
25-75%, about 50-75% or about 75-99% aldehyde concentration.

[0051] In some embodiments, the composition comprises of at least about 1%
glutaraldehyde concentration; at least about 5% glutaraldehyde
concentration; at least about 8% glutaraldehyde concentration; at least
about 10% glutaraldehyde concentration; at least about 20% glutaraldehyde
concentration; at least about 30% glutaraldehyde concentration; at least
about 40% glutaraldehyde concentration; at least about 50% glutaraldehyde
concentration; at least about 60% glutaraldehyde concentration; at least
about 70% glutaraldehyde concentration; at least about 80% glutaraldehyde
concentration; at least about 90% glutaraldehyde concentration; or at
least about 99% glutaraldehyde concentration. In some embodiments, the
composition comprises about 1-30%, about 25-75%, about 50-75% or about
75-99% glutaraldehyde concentration.

[0052] Thickening agents may be added to the forms of the invention
described above. The thickening agents include, for example, dextran,
carboxymethyl cellulose, polyethylene glycol, liposomes, proliposomes,
glycerol, starch, carbohydrates, povidone, polyethylene oxide, and
polyvinyl alcohol. In some embodiments, the thickening agent is dextran,
polyethylene glycol or carboxymethyl cellulose. In some embodiments, the
composition comprises at least about 1% thickening agent concentration;
at least about 5% thickening agent concentration; at least about 10%
thickening agent concentration; at least about 20% thickening agent
concentration; at least about 30% thickening agent concentration; at
least about 40% thickening agent concentration; at least about 50%
thickening agent concentration; at least about 60% thickening agent
concentration; at least about 70% thickening agent concentration; at
least about 80% thickening agent concentration; or at least about 90%
thickening agent concentration. In some embodiments, the composition
comprises at least about 0.5%-10%, at least about 0.5%-25%, or at least
about 0.5%-50% thickening agent concentration. In some embodiments, the
thickening agent can comprise at least about 0.5% of the composition. The
thickening agent can alter a gel time of the composition.

[0053] Some embodiments of the aforementioned aspects of the present
invention may further comprise a radiopaque material. The radiopaque
material includes, for example, bismuth oxide (Bi2O3), zinc
oxide (ZnO), barium sulfate (BaSO4) lanthanum oxide
(La2O3), cerium oxide (CeO2), terbium oxide, ytterbium oxide,
neodymium oxide, zirconia (ZrO2), strontia (SrO), tin oxide
(SnO2), radiopaque glass and silicate glass. The radiopaque glass
includes, for example, barium silicate, silico-alumino barium or
strontium containing glass. The silicate glass includes, for example,
barium or strontium containing glass. In some embodiments, the radiopaque
material comprises at least about 0.001%; at least about 0.05%; at least
about 0.1%; at least about 0.2%; at least about 0.5%; at least about 1%;
at least about 2%; at least about 5%; at least about 8%; or at least
about 10% of the adhesive composition.

[0055] Flexibilizers can be included in the hydrogel composition to
provide flexibility to the material bond upon curing. Flexibilizers may
be naturally occurring compositions or synthetically produced. Suitable
flexiblizers include synthetic and natural rubbers, synthetic polymers,
natural non-native biocompatible proteins (such as exogenous (i.e.,
non-native) collagen and the like), glycosaminoglycans (GAGs) (such as
hyaluronin and chondroitin sulfate), and blood components (such as
fibrin, fibrinogen, albumin and other blood factors).

[0056] The composition as provided herein can optionally include salts
and/or buffers. Examples of the salt include, but are not limited to,
sodium chloride, potassium chloride and the like. Suitable buffers can
include, for example, ammonium, phosphate, borate, bicarbonate,
carbonate, cacodylate, citrate, and other organic buffers such as
tris(hydroxymethyl) aminomethane (TRIS), morpholine propanesulphonic acid
(MOPS), and N-(2-hydroxyethyl) piperazine-N'(2-ethanesulfonic acid)
(HEPES). Suitable buffers can be chosen based on the desired pH range for
the hydrogel composition.

[0057] Additional additives may be present in the formulation to modify
the mechanical properties of the composition. Some additives include, for
example, fillers, softening agents and stabilizers. Examples of fillers
include, but are not limited to, carbon black, metal oxides, silicates,
acrylic resin powder, and various ceramic powders. Examples of softening
agents include, but are not limited to, dibutyl phosphate,
dioctylphosphate, tricresylphosphate, tributoxyethyl phosphates and other
esters. Examples of stabilizers include, but are not limited to,
trimethyldihydroquinone, phenyl-β-naphthyl amine,
p-isopropoxydiphenylamine, diphenyl-p-phenylene diamine and the like.

[0058] One class of additives that may be included in the composition is
nanoparticles or nanometer scale constructions. An example of
nanoparticles that have been engineered to have specific physical
characteristics are nanoshells, as taught by Oldenburg et. al. (U.S. Pat.
No. 6,344,272, incorporated herein by reference in its entirety).
Nanoshells are comprised of a metallic shell surrounding a non-conducting
core; by varying the diameter of the core and the thickness of the shell,
the absorption wavelength of the materials can be tuned to specific
regions of the spectrum. West et. al. discloses the incorporation of
nanoshells into a thermally sensitive polymer matrix for drug delivery in
U.S. Pat. Nos. 6,428,811 and 6,645,517, and further teaches the use of
nanoshells to treat tumors through localized hyperthermia in U.S. Pat.
No. 6,530,994 (the above patents are herein incorporated by reference in
their entirety). The combination of nanoparticles or other nanoscale
structures with the composition of the invention may provide additional
functionality (i.e. tunable absorption spectra) to the composition. In
one example, the composition may be employed to fix the nanoparticles
tuned to absorb near infrared light in a desired physical position prior
to the application of a near-infrared laser to induce local hyperthermia.
The incorporation of the nanoshells in the hydrogel matrix prevents the
leaching of the nanoshells away from the target area.

[0059] The composition may also optionally include a plasticizing agent.
The plasticizing agent provides a number of functions, including wetting
of a surface, or alternately, increasing the elastic modulus of the
material, or further still, aiding in the mixing and application of the
material. Numerous plasticizing agents exist, including fatty acids,
e.g., oleic acid, palmitic acid, etc., dioctylphtalate, phospholipids,
and phosphatidic acid. Because plasticizers are typically water insoluble
organic substances and are not readily miscible with water, it is
sometimes advantageous to modify their miscibility with water, by
pre-mixing the appropriate plasticizer with an alcohol to reduce the
surface tension associated with the solution. To this end, any alcohol
may be used. In one representative embodiment of this invention, oleic
acid is mixed with ethanol to form a 50% (w/w) solution and this solution
then is used to plasticize the polymer substrate during the formulation
process. Whereas the type and concentration of the plasticizing agent is
dependent upon the application, in certain embodiments the final
concentration of the plasticizing agent is from about 0.01 to 10% (w/w),
including from about 2 to about 4% (w/w). Other plasticizing agents of
interest include, but are not limited to: polyethylene glycol, glycerin,
butylhydroxytoluene, etc.

[0060] Fillers of interest include both reinforcing and non-reinforcing
fillers. Reinforcing fillers may be included, such as chopped fibrous
silk, polyester, PTFE, NYLON, carbon fibers, polypropylene, polyurethane,
glass, etc. Fibers can be modified, e.g., as described above for the
other components, as desired, e.g., to increase wettability, mixability,
etc. Reinforcing fillers may be present from about 0 to 40%, such as from
about 10 to about 30%. Non-reinforcing fillers may also be included,
e.g., clay, mica, hydroxyapatite, calcium sulfate, bone chips, etc. Where
desired, these fillers may also be modified, e.g., as described above.
Non-reinforcing fillers may be present from about 0 to 40%, such as from
about 10 to about 30%.

[0061] In certain embodiments, the composition may include a foaming agent
which, upon combination with the crosslinker composition, results in a
foaming composition, e.g., a composition that includes gaseous air
bubbles interspersed about. Any convenient foaming agent may be present,
where the foaming agent may be an agent that, upon contact with the
crosslinking composition, produces a gas that provides bubble generation
and, hence, the desired foaming characteristics of the composition. For
example, a salt such as sodium bicarbonate in an amount ranging from
about 2 to about 5% w/w may be present in the substrate. Upon combination
of the substrate with an acidic crosslinker composition, e.g., having a
pH of about 5, a foaming composition is produced.

[0062] Biologically active agents may be incorporated into the polymer
network of the invention; these agents include but are not limited to
naturally occurring or synthetically produced plasma proteins, hormones,
enzymes, antibiotics, antiseptic agents, antineoplastic agents,
antifungal agents, antiviral agents, anti-inflammatory agents, human and
non human derived growth factors, anesthetics, steroids, cell
suspensions, cytotoxins, cell proliferation inhibitors, and biomimetics
The biologically active agents can be incorporated into the hydrogel of
the invention by any means known in the art. As a non-limiting example,
an agent or multiple agents may be added to the component solutions prior
to mixing such that the hydrogel matrix forms around the agent or
multiple agents and mechanically encapsulates the agent or agents.
Alternatively, the agent or agents may be added to one or all of the
component solutions prior to mixing. In another example, the agent or
agents may be modified or derivatized to react with the components of the
hydrogel and form covalent bonds with the hydrogel. The agent or agents
may be bonded to the backbone of the hydrogel structure in a pendent
chain configuration or as a fully integrated component of the hydrogel
structure. In yet another example, the agent or agents may be suspended
within a hydrophobic domain encapsulated within or distributed throughout
the hydrogel. Alternatively, the agent or agents may be associated with
the backbone of hydrogel through electrostatic, van Der Walls, or
hydrophobic interactions. Combinations of any of the aforementioned
techniques are also contemplated (e.g. a negatively charged agent that is
physically encapsulated in a positively charged hydrogel matrix). The
exact means of incorporation will be dictated by the nature of the
biologically active agent.

Methods

[0063] Aqueous solutions of the component polymers are mixed to form the
hydrogel of the invention. Generally, equal volumes of the aqueous
component solutions are mixed to form the hydrogel. However, different
ratios of the aqueous component solutions may be used provided the
properties of the solutions are such that they crosslink to form the
hydrogel of the invention when mixed. A person skilled in the art can
achieve different curing times for the hydrogel of the invention by
manipulating one or more of the following exemplary parameters:

[0064]
a) the degree of deacetylation of the polysaccharide (e.g., chitosan);

[0065] b) the molecular weight of the polysaccharide (e.g., chitosan);

[0066] c) the species of the aldehyde component of the invention;

[0067]
d) the mass percentage of the polymer components in the aqueous
solutions;

[0068] e) the relative mass percentage of the respective
polymer components in the aqueous solutions;

[0078] In one embodiment of the invention, the hydrogel is formed in situ.
Aqueous solutions of the invention components can be simultaneously
applied or deposited to a target area by spraying, streaming, injecting,
painting or pouring of the solutions. The components mix upon application
to or deposition at the target area and crosslink to form a polymer
network. The formation of the polymer network in an aqueous media creates
the hydrogel. Alternatively, the components may mix in transit to the
target area. This may happen in the air in the case of the aerosolized or
spray application, or in the lumen of a delivery device in the case of a
streaming or injection delivery. The mixing of the component solutions
may be aided by the use of static or active mixing elements in either
delivery, such as inclusion of non-reactive elements to assist in mixing
of the components, e.g., beads. Another method of application would be to
mix the aqueous component solutions prior to delivery provided the cure
time of the hydrogel was appropriately chosen.

[0079] The component solutions may be applied or deposited simultaneously
to the target area, or in iterative fashion (application of an initial
component solution followed by application of a second component
solution, etc.). The method of application or deposition may be any
described above, furthermore, the various methodologies and devices for
performing in situ curing of a multi-component system may be used to
apply the materials of the invention.

[0080] In another embodiment of the invention, the hydrogel is formed
prior to application. The component solutions may be mixed in an
appropriate vessel and allowed cure. The cured hydrogel may then be
removed from the vessel and applied to the target area. Alternatively,
the cured hydrogel may be dried prior to application to the target area.
The term "drying" refers to any process by which the water content of a
candidate polymer material is reduced from an initial value to a lower
value. This may be accomplished by placing the material in an environment
with lower water content than the polymer material under various
temperature and pressure conditions, some of which are listed in Table 1.

[0081] Application of drying techniques beyond those listed herein should
be readily accessible to one of skill in the art. For example, US.
Published Pat. App. No. 2007/0231366 teaches a method of drying a
hydrogel that comprises halting a solution of components undergoing
crosslinking reaction prior to the completion of the reaction by reducing
the temperature of the solution below the freezing point of the reacting
solution, then subsequently freeze drying the partially-crosslinked
hydrogel to remove the solvent from the partially crosslinked hydrogel.
The partially crosslinked hydrogel is then processed through a series of
treatments that serve to complete the crosslinking reaction. The reliance
of this method of fabrication on a phase change between liquid and solid
is cumbersome, and places limits on the production methods that can be
employed in fabricated hydrogels by the taught method. For example, the
timing of the transition of the solution from a liquid to solid state
(i.e. freezing) is highly dependent on the physical and material
characteristics of the mold (wall thickness, heat transfer coefficient,
hydrophilicity or hydrophobicity of the mold surface), the freezing
method (cold plate, freezer, immersion in liquid nitrogen, etc.), and the
rate of the crosslinking reaction among others. Maintaining a consistent
process in the face of these variables is challenging and can provide an
obstacle to the scaled-up production of a hydrogel via the taught method.

[0082] One method for reducing the complexity of the process taught in US.
Published Pat. App. No. 2007/0231366 is to use a method for halting or
slowing the rate of the crosslinking reaction that is not subject to as
many parameters as freezing, such as changing the pH of the solution of
reacting components to a level that does not support further crosslinking
For example, the reaction rate of a second-order nucleophilic
substitution between an N-hydroxysuccinimide and a primary amine
accelerates as the pH of the reaction media becomes more alkaline and
decelerates as the pH of the reaction media becomes more acidic.
Therefore, the addition of an aliquot of an acidic solution at a
sufficient molarity and volume to shift the pH of the reacting media to
an acidic condition will halt or slow the reaction rate of the
nucleophilic substitution. Yet another means of changing the rate of
reaction is by changing the ionic strength of the reaction media. The
solution of hydrogel components is then ready for freeze drying. The
benefit of this novel method is that the alteration of the reaction rate
can be conducted while the hydrogel components are in the liquid phase
(e.g. at room temperature), and is not dependent on the size, shape, or
material of the casting mold. The independence of the method from the
aforementioned limitations will improve consistency of batch-to-batch
production lots by reducing the complexity and user-dependence of the
process steps and lends itself to scale-up production by simplifying the
use of larger molds.

[0083] The use of drying and other processing techniques (i.e. necking,
stretching, machining, cutting, pressing, forming, etc.) can be combined
to impart a shape memory characteristic to the formulation. As an
example, a mold of the composition may be cast in the shape of a
cylindrical tube and subsequently air dried until the moisture content of
the material has reached equilibrium with environment (as determined by
mass or other appropriate methods). The dried formulation may then be
subjected to a necking process in which the dry hydrogel is heated and
stretched to reduce the diameter and increase the length of the cylinder.
When cooled to room temperature, the cylinder retains its necked
dimensions. Upon absorbing water, the cylinder reverts to its cast length
and dimension. The preceding example demonstrates one method of
manipulating the formulation to attain a shape memory feature in response
to hydration; the extension of this concept to other external stimuli
(i.e. pH, ultrasound, radiation, temperature, etc.) should be accessible
to one of skill in the art.

[0084] In one embodiment of the invention, the polysaccharide and
synthetic polymer are dissolved in a neutral or basic buffer. The
crosslinker is dissolved in an appropriately pH balanced buffer. The two
solutions are combined to allow the formation of a hydrogel network
between the polysaccharide, the synthetic polymer, and the crosslinker
The solutions may be mixed as part of the delivery system for use as an
in situ crosslinking material via spray or liquid application, or the
solutions may be cast into a mold after mixing to produce a hydrogel for
subsequent application without further modification, or the resultant
hydrogel may be dried and processed as described previously.

[0085] In a second embodiment, the polysaccharide and synthetic polymer
are dissolved in a neutral or basic buffer along with a visible dye
molecule such as methylene blue, blue dextran, FD&C Blue No. 1, FD&C Blue
No. 2, FD&C Green No. 3, FD&C Red No. 40, FD&C Red No. 3, FD&C Yellow No.
5, FD&C Yellow No. 6, among others. The crosslinker is dissolved in an
appropriately buffered solution. The solutions are mixed as described
above in the prior embodiments to form the hydrogel. The inclusion of the
dye material allows the user to ascertain the thickness and/or location
of the hydrogel at the site of application. As an example, the dye may be
used to infer the thickness of a coating of the hydrogel applied via a
spray or aerosol to a tissue surface by observing changes in the
intensity of the dye color as the thickness of the coating increases. As
another example, the dye may be used to confirm the coverage of a mold or
casting form as a step in a manufacturing process. Alternatively, the
visible dye is present in solution with the crosslinker As yet another
alternative, one or more dyes may be included in the
polysaccharide/synthetic polymer solution and the crosslinker solution.
For example, a blue dye may be added to the polysaccharide/synthetic
polymer solution and a yellow dye may be added to the crosslinker
solution to allow visual confirmation of mixing of the two components, as
the combined solutions will have a green color when well mixed.
Permutations of these techniques with different dyes, combinations of
dyes, inclusion of dyes in one or both of the polysaccharide/synthetic
polymer solutions, and the like to will be clear to one of skill in the
art.

[0086] In a third embodiment, a radio-opaque material may be included with
the polysaccharide and synthetic polymer in a neutral or basic buffer.
Alternatively, the radio-opaque material may be included with the
buffered crosslinker solution, or the radio-opaque material may be
included in both the polysaccharide/synthetic polymer solution and the
crosslinker solution. The solutions are mixed as described above in the
prior embodiments to form a hydrogel that comprises a radio-opaque
element dispersed within the body of the hydrogel. The presence of the
radio-opaque element allows the visualization of the hydrogel via
fluoroscopy when a direct line of sight (i.e. direct visualization) to
the hydrogel is not available. For example, an in-situ crosslinking
embodiment of the invention may be delivered to a patient through a
standard cardiovascular catheter as an embolic agent for the occlusion of
uterine fibroids. The location of the hydrogel may be observed as a dark
or opaque mass on the output of a fluoroscopic imaging system.

[0087] In a fourth embodiment, a thickening agent may be added to either
the neutral to basic solution of polysaccharide and synthetic polymer,
the buffered crosslinker solution, or both solutions. The two solutions
are combined to initiate the crosslinking reaction and form the hydrogel
as described for prior embodiments. The thickening agent may be chosen
such that it does not comprise chemical groups that will react with any
or all of the polysaccharide, synthetic polymer, or crosslinker
components. Alternatively, the thickening agent may be monofunctional, in
that it comprises a single reactive group that can bind to a
complementary chemical group on any or all of the polysaccharide,
synthetic polymer or crosslinker components. The presence of the
thickening agent serves to increase the viscosity of one or both of the
polysaccharide/synthetic polymer and crosslinker solutions. As an
example, a thickening agent may be added to the crosslinker solution if
the polysaccharide/synthetic polymer solution is significantly more
viscous than the crosslinking solution prior to the addition of the
thickening agent. Matching the viscosity of the two component solutions
can improve the mixing of the solutions to produce a more consistent,
homogenous hydrogel structure and reduce variability that may be present
in the rate of the crosslinking reaction due to incomplete or inefficient
mixing among other improvements in handling. As another example, a
thickening agent may be added to either or both of the
polysaccharide/synthetic polymer and crosslinker solutions to produce a
solution that resists migration from the point of delivery prior to
complete crosslinking and formation of the hydrogel. In an exemplary case
of the delivery of an in-situ crosslinking embodiment of the hydrogel, a
highly viscous material will not be washed away, diffused, or otherwise
diluted during the time between delivery and completion of the
crosslinking reaction.

[0088] In a fifth embodiment, a steroid may be combined with a crosslinker
in a neutral to acidic buffer. The polysaccharide and synthetic polymer
are dissolved in a neutral to basic buffer solution. The two solutions
are combined to initiate the crosslinking reaction and form the hydrogel
as described for prior embodiments, entrapping the steroid in the
hydrogel network. Steroids are generally insoluble in basic or alkaline
solutions, therefore the addition of a steroid to the neutral to acidic
buffer containing the crosslinker acts to prevent or mitigate the
precipitation of the steroid out of solution prior the incorporation of
the steroid into the hydrogel. Upon application to a wound, or
implantation into a subject, the steroid will either diffuse out of the
hydrogel at a rate dictated in part by the pore size of the hydrogel, or
it will remain entrapped in the hydrogel until the hydrogel degrades to a
point that allows for diffusion of the steroid into the surrounding
anatomy.

[0089] In a sixth embodiment, an antibiotic such as gentamicin may be
combined with a crosslinker in a neutral to acidic buffer. The
polysaccharide and synthetic polymer are dissolved in a neutral to basic
buffer solution. The two solutions are combined to initiate the
crosslinking reaction and form the hydrogel as described for prior
embodiments, entrapping the steroid in the hydrogel network. Antibiotics
are generally insoluble in basic or alkaline solutions, therefore the
addition of an antibiotic to the neutral to acidic buffer containing the
crosslinker acts to prevent or mitigate the precipitation of the
antibiotic out of solution prior the incorporation of the steroid into
the hydrogel. Upon application to a wound, or implantation into a
subject, the antibiotic will either diffuse out of the hydrogel at a rate
dictated in part by the pore size of the hydrogel, or it will remain
entrapped in the hydrogel until the hydrogel degrades to a point that
allows for diffusion of the antibiotic into the surrounding anatomy.

[0090] In a seventh embodiment, a fully crosslinked form of the
composition of the invention may be used as a carrier for
platelet-rich-plasma (PRP). The fully crosslinked form of the hydrogel is
submerged into a solution of PRP in a state of less than equilibrium
swelling to absorb the PRP into the interstices of the hydrogel network.
The fully crosslinked state of the hydrogel may include but is not
limited to forms such as an air dried form, a fully cured but not yet
dried (semi-hydrated) form, a lyophilized form, and a dried and
fragmented form among others. The PRP-loaded composition of the invention
is then applied to a target anatomy, such as a soft tissue defect (e.g.
tendon, ligament, hernia, rotator cuff, etc.), a laceration or external
wound bed (e.g. pressure sore, diabetic ulcer, etc.), or a hard tissue
defect (e.g. bone) to deliver the PRP to the target area over a specified
period of time. Alternatively, an external material may be used to absorb
and carry the PRP (e.g. gauze sponge, TephaFLEX® knitted monofilament
mesh, TephaFLEX® absorbable film, collagen sponge, bandages, other
scaffold materials, etc.) with the composition of the invention applied
to the surface of the carrier to form a hydrogel coating and act as a
barrier to diffusion of the PRP out of the carrier material. Calcium,
thrombin or collagen may optionally be added to activate the release of
growth factors from the PRP. The method of application may include but is
not limited to a spray application, dip-coating, and painting among
others.

[0091] It should be clear that the examples of incorporating the steroid,
antibiotic, and PRP into the composition of the invention can be extended
to any biologically active agent, including but not limited to naturally
occurring or synthetically produced plasma proteins, hormones, enzymes,
antiseptic agents, antineoplastic agents, antifungal agents, antiviral
agents, anti-inflammatory agents, human and non human derived growth
factors, anesthetics, cell suspensions, cytotoxins, cell proliferation
inhibitors, fibrin, fibrinogen, collagen, and biomimetics.

[0092] In an eighth embodiment, a fiber such as methylcellulose may be
added to the composition to prevent adsorption of the material across the
gastrointestinal track. Methylcellulose may be added to a solution of
fragmented hydrogel in an appropriate buffer for this purpose.

[0093] In a ninth embodiment, a wetting agent such as oleic acid may be
added to either the neutral to basic solution of polysaccharide and
synthetic polymer, the buffered crosslinker solution, or both solutions.
The two solutions are combined to initiate the crosslinking reaction and
form the hydrogel as described for prior embodiments. The wetting agent
serves to promote curing and adhesion of an in-situ composition of the
hydrogel onto an oily target surface such as the skin, liver or gall
bladder.

[0094] In a tenth embodiment, a flexibilizer such as collagen may be added
to either the neutral to basic solution of polysaccharide and synthetic
polymer, the buffered crosslinker solution, or both solutions. The two
solutions are combined to initiate the crosslinking reaction and form the
hydrogel as described for prior embodiments. The type and quantity of
flexibilizer incorporated into the hydrogel composition can be adjusted
to vary the ductility and elasticity of the cured hydrogel.

[0095] In an eleventh embodiment, specific salts and/or buffers can be
used as solvents for dissolving the polysaccharide, synthetic polymer,
and crosslinker. For example, the polysaccharide and synthetic polymer
may be dissolved in a sodium borate buffer adjusted to a neutral or basic
pH. The crosslinker may be dissolved in a sodium phosphate buffer
adjusted to a neutral or acidic pH. The combination of the two solutions
will result in a buffered solution containing the three components of the
hydrogel at a pH that results in a crosslinking reaction rate that is
appropriate for a given application (e.g. gelation in less than 10
seconds for a spray application, gelation in less than 10 minutes for a
casting application, etc.). Specific salts and buffers may be chosen to
accommodate additional components that may comprise the composition of
the invention. For example, monosodium phosphate salt may be used to
achieve an acidic buffer suitable for dissolving both the crosslinker and
a steroid.

[0096] In a twelfth embodiment, a filler such as hydroxyapatite, fibrous
silk, carbon fiber, bone chips, a mesh of polyglycolic acid, a mesh of
TephaFLEX® and the like may be added to either the neutral to basic
solution of polysaccharide and synthetic polymer, the buffered
crosslinker solution, or both solutions. The two solutions are combined
to initiate the crosslinking reaction and form the hydrogel as described
for prior embodiments. The filler serves to alter the mechanical
characteristics of the hydrogel, including but not limited to strength,
toughness, tear resistance, compressive modulus, and tensile modulus.
Alternatively, the polysaccharide and synthetic polymer are dissolved in
a neutral or basic buffer. The crosslinker is dissolved in an
appropriately pH balanced buffer. The two solutions are combined and
poured or sprayed into a mold containing the filler material to allow the
formation of a hydrogel network between the polysaccharide, the synthetic
polymer, and the crosslinker around and/or within the filler.

[0097] In a thirteenth embodiment, a stabilizer such as
trimethyldihydroquinone may be added to either the neutral to basic
solution of polysaccharide and synthetic polymer, or a powder form of the
crosslinker component. The inclusion of a stabilizer serves to extend the
shelf life of the components prior to mixing in the in-situ crosslinking
configurations of the invention. At the point of use, the powder form of
the crosslinker is dissolved in an appropriately pH balanced buffer
solution and combined with the polysaccharide/synthetic polymer solution
to initiate the crosslinking reaction and form the hydrogel as described
for prior embodiments.

[0098] In a fourteenth embodiment, a foaming agent such as sodium
bicarbonate may be added to either the neutral to basic solution of
polysaccharide and synthetic polymer, the buffered crosslinker solution,
or both solutions. The two solutions are combined to initiate the
crosslinking reaction and form the hydrogel as described for prior
embodiments. The presence of the sodium bicarbonate induces the formation
of bubbles and the foaming of the mixture of reacting solutions,
resulting in a hydrogel that exhibits a macroporous structure.
Alternatively, the foaming agent can be added to a mixture of the
polysaccharide/synthetic polymer and crosslinker solutions after the two
solutions have been mixed (while the crosslinking reaction is
progressing). In another method, the foaming agent can be placed in a
mold or cast that receives the combined polysaccharide/synthetic polymer
and crosslinker solutions. The average pore size, distribution of pore
sizes, total pore volume and other characteristics of the foamed hydrogel
can be controlled by adjusting the amount of foaming agent incorporated
into the composition of the invention.

[0099] In a fifteenth embodiment, an absorbent sponge is fabricated by
freeze drying the product of the combination of a neutral to basic buffer
comprising the polysaccharide and synthetic polymer and an appropriately
pH balanced buffer comprising the crosslinker. The sponge may be swelled
in a solution comprising a biologically or pharmaceutically active agent,
and then coated with a in-situ crosslinking formulation of the
composition of the invention. The release of the biologically or
pharmaceutically active agent would be dependent on the size of the agent
relative to the mesh size of the in-situ cured coating. If the size of
the agent is significantly higher than the mesh size of the coating, the
agent would be retained until the coating has substantially degraded or
worn away. If the size of the agent is approximately similar to the mesh
size of the coating, the agent would diffuse out of the sponge at a rate
dictated in part but not limited to the diffusion gradient across the
coating, the tortuosity of the average path through the coating, the
charge of the agent relative to the coating, the thickness of the
coating, and the degree of hydration of the coating, among other
parameters. The coating may be applied using a spraying and/or dip
coating method, as an overmolded casting technique, or other methods
known in the art. The coating may integrate into the surface of the
sponge through covalent bonding, mechanical interlocking, or charge
differences among others. Alternatively, the coating may not integrate
with the sponge and serve as free-floating shell or frictionally bound
shell around a core the sponge material. The coating may be applied to
the core sponge when the sponge is in the hydrated, semi-hydrated, or
dried states. For example, the core sponge may be coated in the dry
state, and the coated sponge may be immersed in a loading solution of
biologically or pharmaceutically active agent. Alternatively, the core
sponge may be immersed in a loading solution of biologically or
pharmaceutically active agent, allowed to dry, then coated in the dry
state. In another example, the core sponge may be immersed in an
appropriate solution to a desired level of hydration and coated, with the
resultant hydrated core, coated material immersed in a second solution
containing a biologically or pharmaceutically active agent. Any of the
above examples may be implanted in the dry, semi-hydrated, or hydrated
states after loading of the coated sponge is substantially complete.

[0100] In another example, a biologically or pharmaceutically active agent
may be incorporated into the polysaccharide and synthetic polymer
solution and/or the crosslinker solution during the fabrication of the
core sponge material. The incorporation may comprise but is not limited
to covalent bonding, electrostatic and/or van Der Walls interactions,
hydrophobic interactions, and entrapment among others. The loaded sponge
material may then be coated with an in-situ crosslinked coating as
described above. The in-situ crosslinked coating may comprise at least
one additional, different, biologically or pharmaceutically active agent
to enable the delivery of at least two different agents from a single
material. The release rates of the agents would be dictated by their
respective diffusion constants through the core sponge and/or the coating
and the degradation rates of the core sponge and/or coating. In another
example, the same biologically or pharmaceutically active agent may be
loaded into the sponge and the core to achieve an extended or modulated
release profile. The release profile can be modified by altering the
degradation times of the sponge and coatings, the density of the hydrogel
network of the sponge and coatings, the relative size of the sponge and
the thickness of the coatings among others. In yet another example, one
agent may be incorporated into the sponge during the fabrication of the
sponge, a second agent may be loaded into the sponge through a swelling
method as previously described, and a third may be incorporated into the
coating. Additionally, layering successive coats of in-situ curing
polymer can be performed to modify the structural, mechanical, and
release profiles of the materials. Each layer may have unique properties
including but not limited to degradation times, method of degradation,
crosslink density, percentage of polymeric material, equilibrium
swelling, ductility, compressive modulus, hydrophilicity, and the like.
It should be obvious to one of skill in the art that permutations of the
structural and mechanical characteristics of the coating and sponge, the
order of loading of the materials with active agents, and the type of
active agents beyond those listed here are achievable.

[0101] In a sixteenth embodiment, the polysaccharide and synthetic polymer
are dissolved in a neutral or basic buffer. The crosslinker is dissolved
in an appropriately pH balanced buffer. The two solutions are combined to
allow the formation of a hydrogel network between the polysaccharide, the
synthetic polymer, and the crosslinker with a gelation time on the order
of tens of minutes. The combined solutions are transferred into a mold
wherein the volume of the solution is less than the volume of the mold.
The mold is then rotated (e.g. using a lathe, centrifuge, or similar
apparatus) to coat the internal walls of the mold with the combined
solution. The rotation of the mold is halted after gelation is complete,
and the hollow, cured hydrogel is removed from the mold. The hollow
hydrogel may be dried at this point by any of the method described
earlier. The cavity in the center of the hydrogel can be used as a
reservoir for a biologically or pharmaceutically active agent, a saline
solution, or the like. The cavity may be filled with a desired solution
prior to or after implantation of the hydrogel into the target anatomy.
The cavity may be refilled with the desired solution via a syringe,
catheter, filling tube, or other mechanism if the solution elutes out of
the material prior to the conclusion of a course of treatment.

Utility

[0102] The compositions described herein may combine multiple utilities as
described below. For example, the hydrogel may be applied or deposited to
prevent leakage across suture lines or anastomoses following therapeutic
or interventional procedures, including coronary artery bypass grafting,
carotid endarterectomy, synthetic graft procedures as described in U.S.
Pat. No. 7,303,757, biopsy as described in U.S. Pat. Nos. 6,350,244,
6,592,608, 6,790,185, 6,994,712, 7,001,410, 7,329,414, and 7,766,891,
liver or kidney transplantation as described in U.S. Pat. No. 7,226,615,
hernia repair, gastric bypass, lung resection, lung volume reduction,
bone void filling, cartilage repair as described in U.S. Pat. Nos.
5,716,413, 5,863,297, 5,977,204, 6,001,352, 6,156,068, 6,203,573,
6,511,511, 6,514,286, and 6,783,712, and topical incisions as described
in U.S. Pat. Nos. 7,371,403, 7,482,503, and 7,776,022 (acting as a
hydrogel bandage), wounds, or ulcers. All recited patents listed in the
preceding paragraph are herein incorporated by reference in their
entirety.

[0103] In ophthalmology, the sealant may be used to seal clear corneal
incisions to provide a soft lubricious surface barrier to protect the
ocular surface incisions from the external environment, such as described
in U.S. Published Pat. App. Nos. 2007/0196454 and 2009/0252781. In
neurosurgery and/or orthopedic surgery, the sealant may be used to repair
dural tears or incisions to ensure a water tight seal preventing CSF
leakage as taught in U.S. Pat. No. 6,566,406. All recited patents listed
in the preceding paragraph are herein incorporated by reference in their
entirety.

[0104] The composition may be used as an embolic for aneurysmal closure.
The form of the invention may include but is not limited to the
following: a liquid composition that crosslinks to form a solid material
in the aneurysm, a dry composition that swells when exposed to liquid
within the aneurysm, and a dry coating placed over a traditional coil to
improve the efficacy and space filling characteristics of the coil. The
composition may be used for the occlusion of neurovascular and/or
peripheral aneurysm or the occlusion of Fallopian tubes and/or seminal
vesicles for sterilization. Additional applications of the composition on
the invention are in varicose vein embolization, uterine fibroid
embolization, embolization of hypervascularized tumors, embolization of
arterio-venous malformations, meningioma embolization, paraganglioma
tumor embolization, and metastatic tumor embolization as taught in U.S.
Pat. No. 7,670,592 and herein incorporated herein by reference in its
entirety. The treatment of tumors may or may not include chemotherapeutic
agents as a component of the hydrogel.

[0105] The composition may be used as a hemostat. One form of the
invention is a solid bandage for hemorrhagic control in trauma in
civilian and military applications as a first responder survival means as
described in U.S. Pat. Nos. 7,371,403, 7,482,503, and 7,776,022. A
further example of the use of the composition of the invention as a
hemostat is to close punctures of the femoral radial or brachial arteries
post catheter based diagnostic or interventional procedures as taught in
U.S. Pat. Nos. 7,331,979, 7,335,220, 7,691,127, 6,890,343, 6,896,692,
7,083,635, 4,890,612, 5,282,827, 5,192,302, and 6,323,278. An additional
example is the management of traumatized, broken, burned, or lacerated
mucosal linings, such as the tonsils post tonsillectomy, adenoids post
adenoidectomy, after tooth removal, to treat dental dry socket, to treat
epistaxis, or treat disruption of any other mucosal surfaces where
bleeding control is required. The composition may be used to provide
hemostatic control post removal of tissue for biopsy purposes as
experienced in liver, lung, kidney, breast, soft tissue, and lymph node
biopsies as taught in U.S. Pat. Nos. 5,080,655, 5,741,223, 5,725,498, and
6,071,301. All recited patents listed in the preceding paragraph are
herein incorporated herein by reference in their entirety.

[0106] The composition may be used to act as an agent for the treatment of
diabetic foot ulcers, venous stasis ulcers, pressure ulcers, or ulcers
and lacerations of any type that require advanced wound management. The
purpose of these materials is to provide a moist environment to cover and
protect the exposed tissue, and sometimes to stimulate optimal healing as
taught in U.S. Pat. Nos. 4,963,489, 5,266,480, and 5,443,950. All patents
listed in the preceding paragraph are herein incorporated herein by
reference in their entirety.

[0107] The composition may be used as an adhesion barrier in general,
gynecologic, and ENT surgical applications to reduce the incidence,
extent, and severity of post-operative adhesions. Adhesions are a type of
scar tissue that forms a connection between two organs or surfaces that
are normally separate in the body. It is hypothesized that the free blood
and plasma that result from surgery can form fibrin strands between
tissues acutely; these strands can mature within a time span of days into
permanent tissue bands which can interfere with normal organ function and
lead to other serious clinical complications. They are sometimes
associated with endometriosis and pelvic inflammatory disease and are
known to frequently form after abdominal, pelvic, or sinus surgery as
taught in U.S. Pat. Nos. 5,852,024, 6,551,610, and 5,652,347. Over 90% of
patients that undergo surgical procedures of this type may form
adhesions. The composition may be formed such that a lumen is maintained
in the body of the composition to enable ongoing airflow (i.e. during
application following sinus surgery) or drainage of fluids. The
composition may also be used as a stent to maintain separation between
tissues. For example, the composition may be formed into a cylindrical
structure and inserted into a sinus ostium that has been dilated to
maintain the dilation of the ostium while the tissue heals. In another
example, the composition may be used as an ethmoid spacer to maintain an
opening into the ethmoid sinuses following surgery. In yet another
example, the composition of the invention may be a cylindrical structure
of freeze-dried hydrogel that is immersed in a solution of a biologically
or pharmaceutically active agent, coated with an in-situ crosslinkable
composition of the invention, and inserted into the frontal or ethmoid
cells to provide local delivery of the biologically or pharmaceutically
active agent. All patents listed in the preceding paragraph are herein
incorporated herein by reference in their entirety.

[0108] The compositions described herein may be used as a surface coating
on medical devices or tissues to prevent the formation of biofilm, and
bacterial or fungal colonies. The selection of a strongly cationic
polysaccharide (e.g., Chitosan) as a component of the hydrogel network
allows for a continuous surface coating on implants and disposable
medical devices that provides a hindrance to biofilm deposition (Carlson,
R. P. et. al., Anti-biofilm properties of chitosan coated surfaces.
Journal of Polymer Science, Polymer Edition, 19(8): pp 1035-1046, 2008).
The mechanism of action may be twofold, the physical structure of the
polysaccharide may function disrupt the bacterial cell wall or the
cationic nature of the polysaccharide may be exploited to bind with
anionic antibiotic agents. Alternatively, a non-polysaccharide component
or additive may be used to provide similar antimicrobial, antibacterial,
or antifungal properties (e.g. silver). An important application of a
surface coated that provides infection control is in the prevention or
treatment of osteomyelitis. Osteomyelitis is an infection of bone or bone
marrow with a propensity for progression due to pyrogenic bacteria. The
presentation of osteomyelitis can be observed due to iatrogenic causes
such as joint replacements, internal fixation of fractures, or root
canalled teeth. The hydrogel composition of this invention could allow
for localized sustained antibiotic therapy. Furthermore, the composition
may be designed to prevent or mitigate bacterial or fungal infections,
reducing or eliminating the need for prolonged systemic antibiotic
therapy as taught in U.S. Pat. Nos. 5,250,020, 5,618,622, 5,609,629, and
5,690,955. All patents listed in the preceding paragraph are herein
incorporated herein by reference in their entirety.

[0109] The compositions described herein can be used effectively to form
porous and non-porous scaffolds of controlled microstructure favorable to
cell seeding and tissue engineering applications. Methods of control of
pore size and structure include the following: freeze drying
(lyophilization), salt extraction, the use of foaming agents such
hydrogen peroxide, and other methods well known in the art. Multiple cell
lines are of contemporary interest to enable the growth and repair of
complex tissues using these porous and non-porous scaffolds such as
vasculature, epithelial tissue, Islet cells for the formation of a tissue
engineered pancreas, nerve regeneration, cartilage regeneration and
repair, bone growth and repair, and connective and soft tissue repair
(ventral and inguinal hernia, pelvic floor reconstruction, vaginal
slings, rotator cuffs, tendon, etc.).

[0110] The hydrogel composition of this invention may used in the
controlled delivery or administration of therapeutic or palliative
agents. The composition may include a synthetic component that acts as a
carrier or depot for the therapeutic or palliative agent. The agent may
be covalently bound to the structure of the hydrogel matrix or physically
entrapped within the hydrogel matrix. The rate of release of the
therapeutic or palliative agents may be controlled by modifying the
composition of the invention. In one example, the composition may be
formed into a hollow chamber to allow injection of a solution containing
therapeutic or palliative agents. The chamber containing the therapeutic
or palliative agents is then placed at the target anatomy (e.g. inserted
into the ethmoid sinus, the frontal sinus cells, agar nasi cells,
maxillary sinus, etc.) and the agent or agents then diffuse through the
wall of the chamber over time. Alternatively, the therapeutic or
palliative agent may be incorporated into the structure of the
composition via bonding or encapsulation. This allows the release profile
of the therapeutic or palliative agents to be modified by either the
diffusion rate of the agent or agents through the hydrogel or the
degradation rate of the hydrogel, or both mechanisms proceeding
concurrently. In another example, the hollow chamber may be inserted into
the target anatomy, then filled with a solution containing the
therapeutic or palliative agents of interest. Targets of contemporary
interest include the following: paclitaxel for the treatment of tumors,
insulin for the treatment of diabetes, analgesics or anesthetics for the
treatment of pain, vasoconstrictors for the control of blood pressure
such as amphetamines, antihistamines, pseudo-ephedrine, and caffeine,
vasodilators for the control of blood pressure such as alpha blockers,
nitric oxide inducers, and papavarine, cholesterol lowering drugs such as
statins (e.g., lovostatin), procoagulants for the control of clotting
such as protamine sulfate, thrombin, fibrin, and collagen, anticoagulants
for the control of clotting such as heparin, coumadin, glycoprotein
2-β-3-α, warfarin, abciximab, Ticagrelor, and clopidogrel
bisulfate, and selective serotonin reuptake inhibitors such as fluoxetine
to provide palliative treatment of depression, obsessive/compulsive
disorders, bulimia, anorexia, panic disorders, and premenstrual dysphoric
disorders, mono amine oxidase inhibitors such as phenelzine for the
palliative treatment of depression, and glucocorticoids for the treatment
of inflammation of the nasal sinus cavity associated with chronic
rhinosinusitis. The hydrogel compositions may be used as a carrier for
synthetic and human-based bone regrowth agents such as recombinant human
bone morphogenic protein as well as biomimetic materials usable for this
indication such as B2A, F2A, PBA, LA1, VA5, PBA, LA1, VA5, B7A, F9A, FSA,
and F20A from BioSurfaces Engineering Technology, heterodimeric chain
synthetic heparin-binding growth factor analogs as taught in U.S. Pat.
No. 7,528,105, positive modulator of bone morphogenic protein-2 as taught
in U.S. Pat. Nos. 7,482,427 and 7,414,028, growth factor analogs as
taught in U.S. Pat. No. 7,414,028, and synthetic heparin-binding growth
factor analogs as taught in U.S. Pat. No. 7,166,574, all of which are
incorporated herein by reference in their entirety.

[0111] The compositions of the current invention have a variety of uses
especially in the area of cosmetic surgery and dermatology. Malleable,
flowable compositions may be prepared as injectable formulations, and are
suitable for superficial to deep dermal augmentation, for example to
correct, fill, and support dermal wrinkles, creases, and folds as well as
lips as taught in U.S. Pat. Nos. 5,827,937, 5,278,201 and 5,278,204.
Larger volume injections can be envisioned for augmentation of breast,
penile glans, and other anatomic positions in the body as taught in U.S.
Pat. No. 6,418,934; all listed patents are incorporated herein by
reference in their entirety.

[0112] Body sculpting procedures, including breast augmentation, are
contemplated for cosmetic and reconstructive purposes. Augmentation of
the glans of the penis is used for treatment of premature ejaculation.
Historically, the main limitation of medical treatment for premature
ejaculation is recurrence after withdrawal of medication. Glans penis
augmentation using injectable compositions of the invention facilitate
treatment of premature ejaculation via blocking accessibility of tactile
stimuli to nerve receptors. The compositions of the invention could also
be used as an injectable bulking agent for sphincter augmentation to
control incontinence. In this application, the material is injected
directly into the sphincter tissue to improve and augment the tissue
structure such that sphincter control could be restored.

[0113] The composition described herein may be used as a space filling
agent and energy barrier to attenuate existing energy-based procedures
and reduce current dose limiting morbidity issues in adjacent tissue. The
hydrogel composition of this invention acts as a transient buffer between
the non-diseased tissue and the tumor target. The benefits of this
approach are twofold; the space filling attribute of the formulation
physically moves the collateral tissue away from the target tumor towards
which the energy is applied, furthermore, the composition may be
formulated to include additives that attenuate the strength of the
applied radiation or other energy. For example, the composition may be
used to mitigate or reduce radiation damage of the prostate during
radiotherapeutic procedures. The displacement of the tumor away from
healthy tissue described herein is also applicable to head and neck
cancer, pelvic, thoracic, breast and soft tissue sarcomas. A further use
of this composition in radiotherapy and surgical tumor removal procedures
is using the composition as a marking system to delineate the boundary of
the tumor.

[0114] The compositions of the current invention may be used to fill voids
in tissue. Potential uses include the treatment of voids in bone, both
weight bearing and non-weight bearing, the treatment of voids or gaps in
articular cartilage, voids caused by a biopsy procedure, and septal
defects of the heart. The treatment of these voids can be enhanced by the
inclusion of biologically active agents and biologically activating
agents in the hydrogel formulation. For example, recombinant human bone
morphogenic protein or allograft human derived bone materials, or
demineralized bone matrices, or synthetic biomimetic growth factor
materials may be incorporated into the composition to aid in the
treatment of bone voids.

[0115] The compositions described herein may be used to adhere two or more
tissues to each other, or to adhere an implant or disposable medical
device to a tissue. For example, a cured, partially hydrated variant of
the formulation may be used to adhere a hearing aid to the ear drum. The
ability of the semi-hydrated hydrogel to conduct pressure waves will
allow the conduction of sound from the hearing aid to the middle ear.
Further applications of the adhesive variants of the composition may
include mucosal or buccal bandages or coverings for laceration of the
dermis.

[0116] The compositions of the current environment can be may be used as a
synthetic synovial fluid or other type of lubricating agent. By
incorporating synthetic polymers that are highly hydrophilic, these
materials may find application in fields such as tendon or ligament
repair and thoracic surgery. The adhesion of a lacerated tendon that has
undergone surgical repair to the tendon sheath reduces the range of
motion of the affected digit or limb and increases the work required to
attain the range of motion that remains. The deposition of a flowable
slurry of the hydrogel composition between the surgically repaired tendon
and the tendon sheath may act to reduce friction and enable a lower work
of extension for the affected tendon. In another application, a thin
layer of the composition may be sprayed onto or otherwise applied to a
tendon to form a lubricous coating that prevents adhesion between the
tendon and the tendon sheath. In thoracic surgery, adhesions may form
after thoracic interventions. The introduction of a hydrogel described
herein may prevent or reduce the formation of adhesions between the
pleura, and in addition, provides a lubricant to movement of the adjacent
tissue past each other.

[0117] The compositions described in the invention may be applied as a
spray coating. The multiple components of the formulation may be applied
sequentially or concurrently to enable curing via partial or full
crosslinking at the target site. Spray coatings may be applied to a
variety of medical devices and implants, including implantable orthopedic
devices, coronary, peripheral, neurovascular stents, catheters, cannulas,
and the like. Additionally, the spray coating may be applied to issues as
a sealant or adhesion barrier, to wounds or lesions to aid in or
accelerate healing or to act as a sealant, as a protective coating for
the eye, or for drug delivery. As a detailed example, an orthopedic
implant may be spray coated with formulations designed to promote
osteogenesis and or osteoinduction and or osteoconduction, to prevent the
formation of bacterial, microbial, or fungal colonies, to assist in the
load bearing characteristics of the implant, or to act as a depot for the
delivery of biologically active or biologically activating agents.

[0118] The compositions described in the invention may be applied as a
liquid for in-situ curing via partial or complete crosslinking. The
multiple components of the formulation may be applied sequentially or
concurrently to enable curing or crosslinking at the target site. These
embodiments may be applied by injecting the formulation into the core or
recesses of implants to be placed in the body to provide local drug
delivery including but not limited to analgesics, antibiotics,
procoagulants, chemotherapeutic agents, and anticoagulants, or tissue
engineering features including but not limited to osteogenesis,
osteoinduction, and osteoconduction. Implants intended for placement in
the body may also be dip coated in the liquid formulations described
herein. These coatings may be allowed to dry for long term storage; they
may be implanted in the dry or rehydrated state. In the dry form, it is
anticipated that the material could be rehydrated in situ. The liquid
formulations may be introduced into a tissue void including but not
limited to bone voids, post biopsy orifices, and septal heart defects.
The liquid formulations may be introduced to augment the shape or form of
existing structures including but not limited to breast, lips, and
naso-labial folds. The liquid formulations may also be used as an embolic
for the treatment of but not limited to neurovascular and peripheral
vascular aneurysms, uterine fibroids, metastatic and benign tumors, and
varicose veins. The liquid formulation may be used to provide protection,
lubrication, and cushioning to the eye following surgery. The liquid
formulation may be used as a method for the delivery or application of
drug, biologic, and biomimetic materials. The liquid formulation is also
useful as sealant for the treatment of but not limited to access to the
dura mater, access to the spine, or access to the vasculature.

[0119] The compositions described in this invention may be applied as a
cured or substantially fully crosslinked material that may or may not be
hydrated. Fields of use for this embodiment of the invention may include
but are not limited to the following: wound healing as a preformed
covering with or without an adhesive backing (as commonly used in bandage
form), as a solid embolic for the treatment of neurovascular or
peripheral aneurysms, uterine fibroids, metastatic and benign tumors, or
varicose veins, as an adhesive to connect two or more tissues or
materials, as an adhesive to attach implants such as a hearing aid to
tissues, and as a method of drug delivery. The non-hydrated, cured
(substantially fully crosslinked), materials may be subsequently
processed (e.g. necking, stretching, forming, cutting, etc.) to attain
other desirable characteristics. These processed materials may be used in
the applications noted in the specification herein. For example, the
hydrogel may be cast as a tube, and necked to a reduced diameter or
profile that facilitates insertion into a tight lumen or limited space
which is generally desirable in the art for minimally invasive and
percutaneaous catheter based medical technologies. One specific example
in which this embodiment would be useful is to control trauma wherein the
cast hydrogel that has been necked would be inserted into narrow tissue
wound formed by the passage of a bullet through said tissue. The material
could be inserted by an emergency room technician in a civilian setting
or a medic in a military setting as a fast acting tourniquet that
facilitates movement of the patient to a more stable medical treatment
environment. It is also contemplated as another example the treatment of
neurovascular aneurysms wherein the non-hydrated, cured material would be
necked to facilitate passage and delivery through the lumen of
microcatheters commonly used in interventional neuroradiology procedures.
The cured, necked hydrogel could then be deposited into the aneurysm
similar to contemporary metallic detachable coils to facilitate closure
or exclusion of the aneurysm.

[0120] The cured (fully or partially crosslinked) compositions described
in this invention may be formulated as a powder. The powder is processed
by being ground, milled, chopped, cryomilled, fragmented through syringe
to syringe mixing, or any other process that may be used to reduce the
size of a material to a desired particle size. The processes may be
undertaken while the material is in the hydrated, partially hydrated, or
non-hydrated forms. Alternatively, spray drying may be used to obtain a
fine powder of the composition by employing hot gas to force a slurry of
the composition out of an atomizer or spray nozzle. The slurry may
contain the components of the composition in an unreacted, partially
reacted, or fully reacted state. In some cases, the individual elements
of the composition may be introduced to the atomizer or spray nozzle
through separate feed lines to prevent the initiation of the crosslinking
reaction prior to passage through the atomizer or spray nozzle. The
partially crosslinked embodiment is particularly suited towards
subsequent in situ or topical reactions where the reaction enables but is
not limited to the following: acting as a sealant, acting as an embolic
agent, acting as a hemostat, acting as a surface coating, acting as a
lubricant, acting as an adhesive, acting as a void filler, acting as a
space filling agent, or any of the other applications covered in this
specification. This embodiment may have application as a topical dressing
with hemostatic properties.

[0121] The compositions described in this invention may be formulated as a
rehydrated powder. The rehydrated powder may consist of the cured
(partially or fully crosslinked) hydrogel material that has been ground,
milled, chopped, cryomilled, fragmented through syringe to syringe
mixing, or any other process that may be used to reduce the size of a
material to a desired particle size and subsequently rehydrated. This
embodiment may have application in the following exemplary areas: the
treatment of diabetic ulcers, the treatment of sinus and mucosal lesions,
as an embolic agent, as a protective coating for tendon, ligament, or the
pleural interface, as a method for drug delivery, as a method for tissue
augmentation (dermal fillers, vocal fold filler, etc.), as a filler for
breast implants, and as a filler for resorbable implants such as those
used for placement against bone and for filling of voids such as between
bones as taught in US. Published Pat. App. 2006/0241777 and herein
incorporated by reference in their entirety.

Kits

[0122] Also provided are kits for use in practicing the subject methods,
where the kits typically include the distinct substrate and crosslinker
components of the composition, as described above. The substrate and
crosslinker components may be present in separate containers in the kit,
e.g., where the substrate is present in a first container and the
crosslinker is present in a second container, where the containers may or
may not be present in a combined configuration. The requisite buffer
solutions for the substrate and crosslinker compositions may be provided
in additional, separate, containers. Containers are understood to refer
to any structure that may hold or surround the components of the hydrogel
composition of the invention; exemplary containers include syringes,
vials, pouches, capsules, carpules, ampules, cartridges, and the like.
The containers may be shielded from visible, ultraviolet, or infrared
radiation through the use of additional components (e.g. a foil pouch
surrounding a syringe) or through selection of the material properties of
the container itself (e.g. an amber glass vial or opaque syringe).

[0123] The subject kits may also include a mixing device, for mixing the
substrates and crosslinking composition together to produce the
composition of the invention. The kits may also include a delivery device
(which may or may not include a mixing element), such as a catheter
devices (e.g. tubes with one or more lumens of identical or differing
sizes and shapes with exit points of varying geometries, dimensions, and
positions), syringe(s) of similar or different diameters and volumes,
spray elements, check valves, stopcocks, Y-connectors, air bleeder
elements (e.g. a membrane that permits the removal of air from a liquid
solution prior to delivery to the patient), inlet ports or chambers for
the introduction of a forced air stream, disposable cartridges that allow
for prolonged deposition of the hydrogel composition, applicators or
spreaders, assemblies for realizing a mechanical advantage in delivering
the composition of the invention, housings or casings to protect and
contain the above mentioned components, and the like.

[0124] The kit may further include other components, e.g., desiccants or
other means of maintaining control over water content in the kit, oxygen
scrubbers or other means of maintaining control over oxygen content
within the kit, an inert gas atmosphere (e.g. nitrogen or argon),
indicators to convey the maximum temperature experienced by the kit,
indicators to convey exposure to sterilizing radiation, ethylene oxide,
autoclave conditions, and the like, retaining or positioning structures
to prevent damage to the components (e.g. trays or packaging card), that
are required to maintain the product in good condition during transport
and storage.

[0125] Examples of a kit for the deployment and in situ formation of the
hydrogel composition of the invention include, but are not limited to:

[0126] Two sealed vials, one containing the nucleophilic component(s) and
the other containing the electrophilic component(s), two syringes, one
containing the buffer for the nucleophilic component(s) and the other
containing the buffer for the electrophilic component(s), a casing for
containing and stabilizing the syringes, a casing for housing and
stabilizing the vials, and a connecter element within the vial housing
that holds needles positioned to pierce the septa on the vials when the
syringe casing and vial casing are mated together. The user fills the
syringes by mating the two casings (driving the needles through the
respective septa), injecting the buffer solutions into the vials, and
withdrawing the reconstituted solutions into the syringes. The user may
then attach a delivery device to the syringes as needed (see exemplary
delivery device elements above for a non-inclusive list).

[0127] A second kit for in situ delivery and formation of the hydrogel
formulation may consist of two dual chamber mixing syringes (e.g. Vetter
Lyo-Ject®); one syringe contains the nucleophilic powder and the
nucleophilic buffer, the other contains the electrophilic powder and
electrophilic buffer, and a syringe casing that houses the two dual
chamber syringes. The user depresses the syringe plungers to transfer the
buffers from the proximal chambers into the distal powder chambers and
reconstitute the powders. The user may then attach a delivery device to
the syringes as needed (see exemplary delivery device elements above for
a non-inclusive list).

[0128] A third kit for in situ delivery and formation of the hydrogel
formulation may consist of a syringe containing the nucleophilic
substrate reconstituted with an appropriate buffer, a sealed vial
containing the electrophilic substrate powder, a second syringe
containing the electrophilic buffer, a casing for containing and
stabilizing the syringes, a casing for housing and stabilizing the single
vial, and a connecter element within the vial housing that holds a needle
positioned to pierce the septum on the vial when the syringe casing and
vial casing are mated together. The user fills the syringes by mating the
two casings (driving the needle through the septum), injecting the
electrophilic buffer solution into the vial, and withdrawing the
reconstituted solution into the syringe. The user may then attach a
delivery device to the syringes as needed (see exemplary delivery device
elements above for a non-inclusive list).

[0129] A fourth kit for in situ delivery and formation of the hydrogel
formulation may consist of a syringe containing the nucleophilic
substrate reconstituted with an appropriate buffer and a sealed chamber
containing the freeze dried electrophilic powder separated by a one way
check valve. Depressing the syringe introduces the nucleophile solution
into the electrophile powder chamber, rapidly reconstituting the
electrophile and beginning the crosslinking reaction. Continued
depression of the syringe pushes the activated solution out of the powder
chamber and into the accessory components (e.g. a mixing element, cannula
or spray tip, etc. as listed above).

[0130] A fifth kit for in situ delivery and formation of the hydrogel
formulation may consist of two syringes, one containing the nucleophilic
substrate reconstituted with an appropriate buffer and the other
containing the electrophilic substrate reconstituted with an appropriate
buffer, and a syringe casing. The user may then attach a delivery device
to the syringes as needed (see exemplary delivery device elements above
for a non-inclusive list).

[0131] A sixth kit for the in situ delivery and formation of the hydrogel
formulation may consist of a sponge or swab containing a dry form of the
polysaccharide substrate, physiologically acceptable polymer substrate,
crosslinking composition, and appropriate buffer salts. The user can
deposit a layer of the cured hydrogel formulation by wetting the swab
with saline and wiping the wet swab across the target tissue or area. The
saline reconstitutes the four components within the swab and begins the
crosslinking reaction; this reaction completes after the activated
components have been deposited at the target, resulting in the formation
of the crosslinked hydrogel formulation. Alternatively, the reaction may
be driven by contacting the swab containing the four components with a
moist tissue surface such as the cornea of the eye.

[0132] Other kits may be envisioned for the use of a hydrogel formulation
that has been cured prior to shipment to the user. The following examples
are non-limiting and are meant to demonstrate the potential for kitting
the hydrogel formulation.

[0133] In one embodiment, a container provides the cured, dried, and
fragmented hydrogel formulation. A syringe is supplied containing a
buffer appropriate for rehydrating the powder. The syringe is connected
to the fragmented hydrogel container and the buffer is introduced to the
container to rehydrate the fragmented hydrogel. The rehydrated hydrogel
formulation is withdrawn into the syringe, at which point the user can
connect it to any of the exemplary device elements previously listed.

[0134] In a second embodiment, both the cured, dried, and fragmented
hydrogel formulation and the appropriate buffer solution are provided in
a dual chamber syringe. The user rehydrates the dry hydrogel fragments by
depressing the syringe plunger and combining the buffer solution with the
dry hydrogel fragments. The user can then connect the syringe to any of
the exemplary device elements previously listed.

[0135] In a third embodiment, the cured, dried and fragmented hydrogel
formulation is provided in a syringe in the rehydrated state. The user
can connect the syringe to any of the exemplary device elements that have
been previously listed.

[0136] In fourth embodiment, the cured, dried and fragmented hydrogel
formulation is provided in a pouch or container for direct application to
the target site.

[0137] In a fifth embodiment, the cured hydrogel may be dried and provided
in any form or geometry. For example, the cured hydrogel may be provided
as a thin cylinder for insertion through a catheter; the same form of
hydrogel may be provided loaded into a catheter or into a cartridge
intended for insertion into a neurovascular catheter. Alternatively, the
cured hydrogel may be provided as a spiral or conical spiral for
insertion into the nasal cavity to prevent nasal valve collapse and
maintain airway patency. In another example, the cured hydrogel may be
provided as a woven stent for prevention of tracheal or nasal passage
collapse, or for the prevention of adhesion formation between the inner
surfaces of a body lumen as taught in U.S. Pat. No. 6,322,590,
incorporated herein by reference in its entirety. In yet another example,
the cured hydrogel may be provided as a sheet for use as a bandage or
dressing. As yet another example, a freeze dried hydrogel formulation may
be attached to an adhesive film for use as a bandage or dressing. In an
additional example, the hydrogel may be coated on a coiled wire and dried
for insertion into a neurovascular aneurysm. When exposed to blood within
the aneurysm, the hydrogel coating swells and takes up a much larger
space than the coil itself or the combination of the coil and dry
hydrogel.

[0138] In a sixth embodiment, the cured hydrogel may be dried and
rehydrated and provided in any form or geometry. For example, the
rehydrated hydrogel may be provided in a sheet for use as a moist wound
covering. In another example, the rehydrated hydrogel may be attached to
an adhesive film as a dressing or moist wound covering.

[0139] In a seventh embodiment, the cured hydrogel may be provided in a
kit with a saline rinse that is pH balanced to accelerate the degradation
of the hydrogel. For example, a freeze-dried hydrogel may be provided as
a sheet for use in adhesion prevention in which the application of the
saline rinse results in a faster degradation of the sheet with respect to
the degradation rate of the freeze-dried hydrogel absent the rinse.

[0140] In addition to above-mentioned components, the subject kits
typically further include instructions for using the components of the
kit to practice the subject methods. The instructions for practicing the
subject methods are generally recorded on a suitable recording medium.
For example, the instructions may be printed on a substrate, such as
paper or plastic, etc. As such, the instructions may be present in the
kits as a package insert, in the labeling of the container of the kit or
components thereof (i.e., associated with the packaging or subpackaging)
etc. In other embodiments, the instructions are present as an electronic
storage data file present on a suitable computer readable storage medium,
e.g. CD-ROM, diskette, etc. In yet other embodiments, the actual
instructions are not present in the kit, but means for obtaining the
instructions from a remote source, e.g. via the internet, are provided.
An example of this embodiment is a kit that includes a web address where
the instructions can be viewed and/or from which the instructions can be
downloaded. As with the instructions, this means for obtaining the
instructions is recorded on a suitable substrate.

EXAMPLES

[0141] The following examples are put forth so as to provide those of
ordinary skill in the art with a complete disclosure and description of
how to make and use the present invention, and are not intended to limit
the scope of what the inventors regard as their invention nor are they
intended to represent that the experiments below are all or the only
experiments performed. Efforts have been made to ensure accuracy with
respect to numbers used (e.g. amounts, temperature, etc.) but some
experimental errors and deviations should be accounted for. Unless
indicated otherwise, parts are parts by weight, molecular weight is
weight average molecular weight, temperature is in degrees Centigrade,
and pressure is at or near atmospheric.

Example 1

[0142] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 10:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. An equal volume of a multi-armed polyethylene
glycol with ester active groups reconstituted in sodium borate buffer at
a 2:1 ratio of polyethylene glycol ester to polyethylene glycol amine was
mixed with the chitosan solution. After one hour had passed, a firm,
clear hydrogel had formed (FIG. 4).

Example 2

[0143] Three samples were sectioned from a hydrogel fabricated as
described in Example 1, weighed, and placed in phosphate buffered saline
at 37 C. After twenty four hours had passed, the samples were weighed and
the amount of swelling over that time period was calculated as:
100*(m24-m0)/m0, where m0 is the mass of the sample at time zero and m24
is the mass of the sample at twenty four hours. The hydrogels had swelled
an average of 143% during over a period of twenty four hours.

Example 3

[0144] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 10:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. An equal volume of sodium phosphate buffer
containing 4% glutaraldehyde (GA) was combined with the chitosan
solution. After one hour had passed, a firm, yellow-brown gel had formed
(FIG. 5).

Example 4

[0145] A multi-armed polyethylene glycol with amine active groups was
combined with carboxymethylcellulose (CMC) at a 4:1 ratio of polyethylene
glycol to carboxymethylcellulose in sodium borate buffer. An equal volume
of a multi-armed polyethylene glycol with ester active groups
reconstituted in sodium borate buffer at a 1:1 ratio of polyethylene
glycol ester to polyethylene glycol amine was mixed with the
carboxymethylcellulose solution. After one hour had passed, a soft, clear
hydrogel had formed (FIG. 6).

Example 5

[0146] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 5:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. An equal volume of a multi-armed polyethylene
glycol with ester active groups reconstituted in sodium borate buffer at
a 2:1 ratio of polyethylene glycol ester to polyethylene glycol amine was
mixed with the chitosan solution. After one hour had passed, a firm,
clear hydrogel had formed. The hydrogel was dried to a constant mass and
ground into particulate with a cryogrinding process. An image of the
cryomilled particulate is shown in FIG. 7.

Example 6

[0147] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 5:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. An equal volume of a multi-armed polyethylene
glycol with ester active groups reconstituted in sodium borate buffer at
a 2:1 ratio of polyethylene glycol ester to polyethylene glycol amine was
mixed with the chitosan solution, and the combined solutions were cast
into a tray to a depth of approximately 3 mm. The sample was subjected to
freeze-drying, after which a 1 cm by 1 cm sample was cut from the larger
sample. The material had the consistency of a sponge or dense gauze; it
could be manipulated with operations like rolling, pressing, and folding
without noticeable damage or tearing. FIG. 8 shows the sample material
rolled on itself and held in a pair of forceps.

Example 7

[0148] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 15:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. An equal volume of a multi-armed polyethylene
glycol with ester active groups reconstituted in sodium borate buffer at
a 2:1 ratio of polyethylene glycol ester to polyethylene glycol amine was
mixed with the chitosan solution, and the combined solutions were cast
into a cylindrical mold 0.25'' in diameter. The composition was allowed
to cure, then it was removed from the mold and air dried to a constant
mass and outer diameter of 0.114''. The diameter of the rod was further
reduced to 0.033'' from its cast dimension via a necking process. A
sample of the necked rod was cut to a length of 0.5'' and placed in
water; the mass, length, and diameter of the sample was tracked over
time. At approximately 24 hours of exposure to water, the sample had
exhibited a 1285% increase in mass, a 44% decrease in length, and a 481%
increase in diameter. FIG. 9 shows a sample of the material in the dry
and hydrated states.

Example 8

[0149] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 5:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer with methylene blue as a colorant. This solution
was loaded into a 1 milliliter syringe. An equal volume of a multi-armed
polyethylene glycol with ester active groups reconstituted in sodium
phosphate buffer at a 2:1 ratio of polyethylene glycol ester to
polyethylene glycol amine was loaded into a second 1 mm syringe. The
syringes were joined to a syringe handle, overmolded connector, mixing
element, and spray tip. The delivery system was used to apply a thin,
conformable coating of the hydrogel composition to a human hand that
cured within seconds of application. The coating was able to adhere to
the skin when held in a vertical orientation and could withstand flexure
of the palm without rupture or cracking (FIG. 10).

Example 9

[0150] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 9:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. This solution was loaded into one of the two
barrels on a dual syringe applicator. An equal volume of a multi-armed
polyethylene glycol with ester active groups was reconstituted in sodium
phosphate buffer at a 2:1 ratio of polyethylene glycol ester to
polyethylene glycol amine. Methylene blue was added to the sodium
phosphate solution for visualization purposes and the solution was loaded
into the second barrel of the dual syringe applicator. The dual syringe
applicator was combined with plunger caps, a dual syringe plunger, and a
spray tip.

[0151] A section of explanted bovine tendon and an intacted section of the
tendon sheath was cut to approximately 3 inches in length. The tendon was
advanced out of the sheath until approximately 1.5 inches of the tendon
was exposed. The delivery system was used to apply a thin
(sub-millimeter), conformable coating of the hydrogel composition to the
outer surface of the tendon. After four seconds, the tendon was retracted
into the sheath using a pair of forceps. The coating was lubricious and
non-friable, remaining intact and adherent to the tendon over the course
of 20 extension/retraction cycles. FIG. 11 shows a cross sectional image
of the bovine tendon with the coating identified by an arrow.

Example 10

[0152] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 17:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. This solution was loaded into one of the two
barrels on a dual syringe applicator. An equal volume of heat treated
glutaraldehyde and dextran was reconstituted in sterile water for
injection at a heat treated glutaraldehyde:polyethylene glycol ratio of
1:42.5 and a dextran:polyethylene glycol ratio of 1:10 polyethylene
glycol. The heat treated glutaraldehyde/dextran solution was loaded into
the second barrel of the dual syringe applicator. The dual syringe
applicator was combined with plunger caps, a dual syringe plunger, and a
spray tip. The delivery system was used to apply a thin, conformable
coating of the hydrogel composition to a human hand. The coating was able
to adhere to the skin when held in a vertical orientation and could
withstand flexure of the palm without rupture or cracking. FIG. 12 shows
a perspective view of the coating as adhered to the skin.

Example 11

[0153] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 9:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. An equal volume of a multi-armed polyethylene
glycol with ester active groups reconstituted in sodium borate buffer at
a 2:1 ratio of polyethylene glycol ester to polyethylene glycol amine was
mixed with the chitosan solution, and the combined solutions were cast
into a tray to a depth of approximately 3 mm. The sample was subjected to
freeze-drying, after which a 1 cm by 1 cm sample was cut from the larger
sample. The sample was placed in a solution of sterile saline to swell
for 1 hour.

[0154] Concurrently, a kit for the application of a spray coating of the
composition was prepared by fabricating a solution of a multi-armed
polyethylene glycol with amine active groups was combined with chitosan
at a 22:1 ratio of polyethylene glycol to chitosan in an alkaline
solution of FD&C Blue No. 1 in sodium borate buffer. This solution was
loaded into one of the two barrels on a dual syringe applicator. An equal
volume of a multi-armed polyethylene glycol with ester active groups was
reconstituted in sodium phosphate buffer at a 2:1 ratio of polyethylene
glycol ester to polyethylene glycol amine. The dual syringe applicator
was combined with plunger caps, a dual syringe plunger, and a spray tip.

[0155] The rehydrated hydrogel was removed from the sterile saline and the
dual syringe applicator was used to apply a coating of the in-situ
crosslinking form of the composition onto the surface of the hydrogel.
FIG. 13. shows a cross section of the coated hydrogel with a ruler as a
reference; the scale on the ruler is in millimeters. The coating appeared
to adhere and integrate into the surface of the hydrogel, and did not
delaminate or fracture when flexed or bent. FIG. 14. shows a cross
section of the coated hydrogel held by forceps in a double-over
configuration. The coated hydrogel was returned to the sterile saline for
24 hours. At the end of this time, the hydrogel coating had swelled to a
degree notable via visual inspection, however, the coating had not
fractured, delaminated, or developed any fissures or irregularities.

Example 12

[0156] A multi-armed polyethylene glycol with amine active groups was
combined with chitosan at a 9:1 ratio of polyethylene glycol to chitosan
in sodium borate buffer. An equal volume of a multi-armed polyethylene
glycol with ester active groups reconstituted in sodium borate buffer at
a 2:1 ratio of polyethylene glycol ester to polyethylene glycol amine was
mixed with the chitosan solution, and the combined solutions were cast
into a cylindrical mold. The volume of the combined solution was less
than that of the mold. The mold was fixed in a lathe and spun to coat the
internal walls of the mold with the solution. When the hydrogel had
cured, the mold was removed from the lathe and opened to allow the
hydrogel to dry and form a hollow, balloon like structure. FIG. 15. shows
the hydrogel structure at end of the drying period.

[0157] The preceding merely illustrates the principles of the invention.
It will be appreciated that those skilled in the art will be able to
devise various arrangements which, although not explicitly described or
shown herein, embody the principles of the invention and are included
within its spirit and scope. Furthermore, all examples and conditional
language recited herein are principally intended to aid the reader in
understanding the principles of the invention and the concepts
contributed by the inventors to furthering the art, and are to be
construed as being without limitation to such specifically recited
examples and conditions. Moreover, all statements herein reciting
principles, aspects, and embodiments of the invention as well as specific
examples thereof, are intended to encompass both structural and
functional equivalents thereof. Additionally, it is intended that such
equivalents include both currently known equivalents and equivalents
developed in the future, i.e., any elements developed that perform the
same function, regardless of structure. The scope of the present
invention, therefore, is not intended to be limited to the exemplary
embodiments shown and described herein. Rather, the scope and spirit of
present invention is embodied by the appended claims.